No start with a no bus message?

Hello, I have the network diagrams pulled up for you. There is a splice connector (J/C 3) which is a junction connector for the modules on the bus, its a really simple network. The service info has some voltage readings you can look for, Ill post all this next. Look for battery voltage on at least on pin at the data link connector, pin 16 is power with the key On.

yes

Ok here are the network diagrams, these are from 2000, so there can be mistakes, but its simple enough. Here are some checks you can do right at the DLC with a multimeter. With the key On, Id be interested in the readings from pins 3 and 11. I will post further info as we go here.

Read this theory of operations, notice the network wires are going to be a twisted pair. By the Bus Failure Messages(2nd diagram) it shows what certain voltage levels can mean, this is very helpful. I would also go around and check every Grounding location, any green/whitish crusties in ground wires is a fail. You can voltage drop from B+ terminal to the Alternator to battery wire, so testing positive to positive, see what you get for voltage drop while cranking. you can do this with the Ground side as well, from battery negative to the engine block, frame, body etc. You should not see much of anything, you want as close to zero volts as possible.
Check bulk connectors for corrosion inside the pins. This car is pretty old now, so wiring issues are not surprising. But go through this, see what you have, make sure your meter has a good ground when testing, check it with known good power.

pins 3 and 11 at the dlc read 2.8 volts and when checking the 5 volt circuit at the tps i got a reading of 5.7 volts. is that ok?

on the 5volt reference wire? No thats not good, should not be over 5 volts. TPS is almost always 5volt ref. let me pull some wiring diagrams.
What did you use as your grounding location?
With an odd voltage like that, I would see what happens when you use the sensor's ground instead of battery negative.
But if thats really a 5.7volt reading I will grab the PCM diagrams and we can be sure. When I get things like this, the first things that come to mind are a failing voltage regulator, except you replaced the ECM already. So we may be looking at voltage bleeding over from corrosion inside a connector somewhere. You should see if you have 5.7v at the ECM on that same wire, we can then isolate some things. The 2.8volts at the DLC is a little high. But with a multimeter is can only sample the voltage so fast, it has a limit. So a meter will average out your reading. I will get the ECM wiring diagrams ready for you. brb

Unplug a temp sensor and see if you have 5volts on one of the two wires.

here is a clearer diagram of the network topology. Hopefully its a bit cleaner.
Do you get a Check Engine light with the key On?

these are the oem diagrams for the MAP, TPS, CRK, CAM, and 5vRef along with the PCM connector pinouts. Let us know what you find. Have a nice night.